DAMAGE AND FAILURE ANALYSIS OF BRITTLE MATERIALS BY ACOUSTIC-EMISSION

Application of stress or changes in environmental conditions can cause a material such as concrete or rock to become damaged, thereby affect ing the performance of the structure. Because damage processes produce microseismic events called acoustic emission (AE), the growth of dama ge and the onset of failure can be identified by monitoring AE. In par ticular, a probability density function of acoustic emission events wa s used to describe the development of damage. It was observed that mor e porous or cracked materials displayed a higher AE rate than less por ous or cracked materials at the same percentage of the maximum stress prior to failure. This suggests that the AE technique may be applied t o diagnose the level of damage in a brittle material and may be useful to select materials for certain applications. Also, the experimental results indicated that the average root-mean-square value from a numbe r of AE signals could be used as a real-time monitoring tool to predic t the onset of failure.